1. Field of the Invention
The present invention relates to a holder for holding wafer-like articles without physical contact between the holder and the wafer-like article being held. More particularly, the present invention relates to an apparatus for holding articles through the use of a particular fluid dynamic relationship between the wafer-like article and the holder created by the structure of the holder.
2. Description of the Prior Art
The handling of wafer-like articles, such as silicon wafers, can present problems. Some prior art wafer-like article holding, apparatus have mechanical latches to hold the article in place. The mechanical latches have drawbacks such as contact between the article and the holder. The contact can cause contamination of the article as well as induce mechanical stresses in the article.
Other prior art wafer-like article holders include vacuum or electrostatic chucks. These types of holders also have drawbacks. Such drawbacks include physical contact between the holder and the article which can cause contamination and mechanical damage. Also, because some actual pre-processed articles, such as wafers, are not flat, securing such articles on a flat holder by vacuum or electrostatic means can cause mechanical stresses in the article.
U.S. Pat. No. 5,080,549 discloses a wafer handling apparatus operating under the Bernoulli principle to pick up, transport and deposit wafers. The apparatus includes a plate that has a plurality of laterally oriented outlets and a central outlet for discharging gas in a pattern sufficient to develop a low pressure environment to pick up the wafer while bathing the wafer in radially outflowing gasses to prevent intrusion and deposition of the wafer of particulate matter in suspension. The pressure differential caused by the Bernoulli principal serves to lift the wafer without any physical contact whatsoever between a wand assembly and the top or bottom surfaces of the wafer.